1. Field of the Invention
The present invention relates to air filtering and separating devices and, more particularly, to a separator device for the removal of oil from an air stream carrying a mist of oil droplets.
2. Description of the Prior Art
Oil separators of the above-mentioned type are used primarily in connection with the reclamation of the oil mist which is contained in the compressed air produced by rotary compressors, especially screw-type compressors, which require the oil for lubrication. The size of the oil droplets which are to be removed from the air is comparatively small and extends into the region of aerosol-type mist, with a droplet size of less than 0.1 .mu.m. In order to achieve a greater degree of oil removal, it has already been suggested that oil separators be designed to operate in consecutive filtering stages, the air flowing first through a separator element with a comparatively coarse structure and, from there, through a second separator element with a finer filter body structure.
One such prior art oil separator is known from the British Pat. No. 988,692. This oil separator features two concentrically spaced tubular separator elements through which the oil-carrying air stream is forced to flow in a radial direction. The two separator elements are of fine and coarse structure, respectively, but, contrary to what one might expect, the first, outer filter element has a fine glass fiber structure, while the second, inner filter element has a coarser wire mesh structure. An annular gap separates the two cylindrical filter elements.
This prior art device is intended to produce an oil separating action in which the fine droplets are collected into larger oil droplets by the first separator element, whereupon the larger droplets are carried by the air stream, across the intermediate air gap, to the coarser separator element which holds and further collects the droplets, allowing them to flow downwardly into a collecting chamber. The upper and lower ends of both separator elements are formed by common top and bottom plates, and it is thus necessary for the oil which has collected in the space between the inner and outer separator elements to traverse the inner element, in order to reach the collection chamber from which it can be removed via a suction pipe. While the collection chamber for the oil is separated from the outflowing air stream by an axial cover panel, the device does not include any means which prevent a certain capillary action of the inner separator element on the oil which has accumulated in the bottom portion of the space between the outer and inner elements, thereby lifting some of that oil back into the air stream.